The Trump administration is showing no signs of backing down from an executive order barring citizens from seven Muslim-majority countries from entering the U.S., but ever-changing details about how the sweeping new rules should be enforced are sowing chaos and confusion.

Trump issued the order early Friday evening, creating confusion for travellers over the weekend as foreign governments tried to grapple with how the rules would affect their citizens.

For Canadians, the U.S. State Department initially said the ban covered dual citizens of Canada and any of the seven countries β€” Syria, Sudan, Iran, Iraq, Libya, Yemen and Somalia. By Saturday night, the Prime Minister's Office assured all Canadian citizens they could move freely across the border. By Sunday afternoon, the scope was widened to include all Canadian permanent residents.

It's still not entirely clear what this means for dual nationals in other countries.

The U.K. foreign office put out a statement saying U.K. citizens who share nationality with any of the banned countries can travel freely to the U.S., but will face extra security checks if they are travelling directly from one of the blacklisted countries.

But on the ground, some people's stories appeared to contradict the official line. One Scottish national who has an Iranian passport was not permitted to fly home from a Costa Rican holiday via New York, the BBC reports

'Case-by-case basis'

Green card holders who have passports from the seven countries were originally told they would be banned, but U.S. officials told The Associated Press on Sunday said they would be processed  on a "case-by-case" basis."

Later, Homeland Security Secretary John Kelly issued a statement saying: "I hereby deem the entry of lawful permanent residents to be in the national interest."

Green card holders are considered permanent residents in the U.S. 

Nevertheless, Kelly reiterated that U.S. permanent residents trying to enter the country would be dealt with on a case-by-case basis.

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More than 1,000 people gathered at Seattle-Tacoma International Airport to protest Trump's order that restricts immigration to the U.S. Protesters gathered at airports across the country over the weekend. (Genna Martin/Associated Press)

'We're really in a crisis mode'

Meanwhile, chaos and outrage reigned across the country Sunday, with travellers detained at airports, panicked families searching for relatives, and protesters registering opposition to the sweeping measure that was blocked by several federal courts.

Attorneys struggled to determine how many people had been affected so far by the rules, which Trump said Saturday were "working out very nicely."

Critics described widespread confusion, with an untold number of travellers being held in legal limbo because of ill-defined procedures.

Lawyers manned tables at New York's Kennedy Airport to offer help to families whose loved ones had been detained, and some 150 Chicago-area lawyers showed up at O'Hare Airport after getting an email asking for legal assistance on behalf of travellers.

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President Donald Trump's advisers say a federal judge's emergency order 'really doesn't affect' his efforts to temporarily bar refugees and citizens of seven predominantly Muslim countries from entering the U.S. (Stephen Lam/Getty Images)

"We just simply don't know how many people there are and where they are," said Lee Gelernt, deputy director of the American Civil Liberties Union's Immigrants' Rights Project.

The executive director of National Immigration Law Center, Marielena Hincapie, said "this is just the beginning."

"We're really in a crisis mode, a constitutional crisis mode in our country, and we're going to need everyone," she said. "This is definitely one of those all-hands-on-deck moments."

Trump team doubles down

Chief of Staff Reince Priebus on Sunday insisted there wasn't chaos at U.S. airports and he would "apologize for nothing."

"I mean, the fact of the matter is 325,000 people from foreign countries came into the United States yesterday and 109 people were detained for further questioning. Most of those people were moved out," he told NBC's Meet the Press on Sunday.

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Protesters rally during a demonstration against the new immigration ban affecting people from seven Muslim-majority countries at John F. Kennedy International Airport on Saturday. (Stephanie Keith/Getty Images)

4 states move to block order enforcement

U.S. judges in at least four states blocked federal authorities from detaining or deporting citizens from those countries who have U.S. visas or green cards or who are refugees.

Judges in Massachusetts, Virginia and Washington state, each home to major international airports, issued their rulings late Saturday or early Sunday, following an order on Saturday night by U.S. District Judge Ann Donnelly in New York's Brooklyn borough.

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Demonstrators block traffic at the international arrival terminal as they protest against the immigration ban affecting several Muslim-majority countries at San Francisco International Airport on Saturday. (Stephen Lam/Getty Images)

Donnelly had ruled in a lawsuit by two men from Iraq being held at John F. Kennedy International Airport.

While none of the rulings struck down the executive order, the growing number of orders could complicate the administration's effort to enforce it.

The ACLU estimated the ruling would help as many as 200 people who have valid visas, but were caught up after the executive order at airports across the U.S.

The U.S. Department of Homeland Security issued a statement Sunday saying they are "committed to ensuring that all individuals affected by the executive orders, including those affected by the court orders, are being provided all rights afforded under the law."

"We are also working closely with airline partners to prevent travellers who would not be granted entry under the executive orders from boarding international flights to the U.S. Therefore, we do not anticipate that further individuals traveling by air to the United States will be affected," the statement read.

Some Republicans against ban on Muslims 

Republican Senators John McCain and Lindsey Graham said on Sunday that Trump's order may do more to help recruit terrorists than improve U.S. security.​

"Ultimately, we fear this executive order will become a self-inflicted wound in the fight against terrorism," they said in a statement, adding that the U.S. should not stop green card holders "from returning to the country they call home."

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A woman greets her mother after she arrived from Dubai on Emirates Flight 203 at John F. Kennedy International Airport in Queens, N.Y. (Andrew Kelly/Reuters)

Trump responded in a tweet, calling the pair "weak on immigration."

Order 'incompetent, ineffective': Democrats

Protests were held at airports across the U.S. on both Saturday and Sunday against Trump's decision, which he announced one week into his presidency, framing it as important to fight terrorism.

Jay Inslee, the Democratic governor of Washington state, said Trump's order could have damaging consequences.

"This is probably the most incompetent, ineffective, unconsciously provocative and dangerous action of any government I have ever seen, and it's very disappointing to see our federal government create chaos in our nation."

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At the Los Angeles International Airport, Homa Homaei, a U.S. citizen from Iran, is hugged by a lawyer working to help her Iranian family members affected by the travel ban. (Patrick T. Fallon/Reuters)

With files from Associated Press and Reuters